By Joseph Arroyo
Updated May 20, 2020

Although Medicare provides affordable health insurance for millions of Americans, the program itself can be a cause of confusion. Many people are eager to know when their coverage begins and when they can make changes to it.

In this guide, we'll review the basics of Medicare eligibility. We'll also look at the specifics of when your coverage begins. Plus, we'll touch on when the Medicare Annual Enrollment Period is and what that means to you.

When Does Medicare Start?

Knowing when your Medicare coverage actually starts is an important part of planning for the future. You can think of starting Medicare coverage in two steps:

  • Being eligible for the program

  • Entering the program and starting your coverage

The easy thing to remember is that Medicare always starts on the first day of a given month. Everyone who enters Medicare begins their coverage on the first day of the month they enter the program.

You'll start your coverage on the first day:

  • Of the month you turn age 65

  • Of the month after you enroll in Medicare if you've worked past age 65 and are leaving your employer-provided health insurance

  • Of the 25th consecutive month you receive Social Security disability income

  • Of the fourth month you've undergone dialysis after being diagnosed with end-stage renal disease (ESRD)

  • Of the fifth month after being diagnosed with Lou Gehrig's Disease (ALS)

In each of these cases, you'll receive your Medicare card in the mail before your coverage begins. If you enroll in a private option such as Medicare Supplement or Medicare Advantage, this coverage will start at the same time as Original Medicare (Medicare Part A and Part B).

When Does Medicare Open Enrollment Start?

Most people in Medicare can make changes to their coverage once per year. The technical term for this period is the Medicare Annual Enrollment Period (AEP).

AEP occurs at the same time each year: October 15 to December 7.

When you make a change during the AEP, your coverage is adjusted for the next year. So, if you switch Medicare plans in November 2020, the change will take effect on January 1, 2021.

During the AEP, you can make a number of changes to your coverage:

  • Switch from Original Medicare to Medicare Advantage

  • Change from one Medicare Advantage plan to another

  • Add a prescription drug plan

  • Change from one prescription drug plan to another

  • Drop Medicare Advantage and return to Original Medicare

  • Drop Medicare Advantage, return to Original Medicare, and enroll in Medicare Supplement insurance (if your application is approved)

During AEP, you can make an unlimited number of changes to your coverage. The last plan applied for by the deadline (December 7) will become effective on January 1. So, if you apply for one plan early on in the AEP, but learn about another plan with better coverage, you can still enroll in it, even though you've already chosen a different plan.

Remember, AEP is for people who already have Medicare coverage. You are changing your coverage during this period, not signing up for the first time.

Besides the Annual Enrollment Period, you may be able to make changes to your coverage in special circumstances. Moving out of your plan's service area qualifies you for a Special Election Period, as does gaining or losing Medicaid coverage.

During a Special Election Period, you have the ability to make a single change to your Medicare coverage.

Learn about Medicare plan options in your area

When Does Medicare Begin?

Earlier, we discussed when your coverage starts. After gaining eligibility, your coverage begins on the first day of the month. In this section, we'll review when you become eligible for Medicare.

There are two sets of criteria for Medicare eligibility:

  • Citizenship or residence requirements

  • Event requirements (age, disability status, and certain diagnoses)

Medicare Citizenship or Residence Requirements

To be eligible for Medicare, you must be a US citizen or a permanent legal resident. If you're a permanent legal resident, you must have legally resided in the US for five consecutive years. If you don't meet either of these requirements, you won't enter Medicare.

Medicare Event Requirements

Assuming you meet the citizenship requirement, there are a few life events that qualify you for Medicare. You will become eligible to enter Medicare when:

  • You turn age 65 (aging into Medicare)

  • You have received Social Security, Railroad Retirement Board, or disability income for 24 consecutive months

  • You have been diagnosed with Lou Gehrig's Disease (ALS)

  • You have been diagnosed with end-stage renal disease (ESRD)

Most people enter Medicare by turning 65. When this is the case, you'll have a seven-month window to enroll. The window, called the Initial Coverage Election Period (IEP or ICEP), is centered around your 65th birthday. You can enroll at any time in the:

  • Three months before your birthday month

  • The month you turn 65

  • Three months after the month you turn 65

During your IEP, you can enroll in Original Medicare and choose Medicare Advantage, prescription drug (Medicare Part D) coverage, or Medicare Supplement (Medigap) insurance.

If you don't enroll during this seven-month window, your enrollment will be considered late. You may have to pay a late enrollment penalty.

In addition to paying the penalty premium, you won't be able to enroll in Medicare until the General Enrollment Period (GEP), from January 1 to March 31 of every year. If you enroll during the GEP, your coverage will start on July 1.

You can also enroll in Medicare Advantage or prescription drug coverage during the GEP. Medicare Supplement insurance has slightly different rules, but you might be able to enroll in that during GEP, too.

Taking Steps Before Medicare Starts

We started by answering the question, "when does Medicare start?" We also reviewed the specifics of when you become eligible for Medicare and when you can make changes to it. To get the most out of Medicare, it pays to do some research before your coverage begins.

Joseph Arroyo is a licensed Medicare insurance agent who lives in Hilton Head, South Carolina. Arroyo is certified to sell Medicare products including Medicare Supplement insurance, Medicare Advantage, and prescription drug plans.